easc lec 3

Composition of the earths layers

• Crust

• Mantle

• Core

Physical properties of the earth’s layers

• Continental crust

• Oceanic crust

• Lithosphere

• Asthenosphere

• Mesosphere

• Outer core

• Inner core

Crust

Less dense silicate materials

Mantle

Dense silicate materials

Core

Metalic

• Fe + Ni + S

Lithosphere (uppermost mantle)

Broken into plates that push apart

• Made of the crust & mantle

Asthenosphere (upper mantle)

• Ductile

• Moves

• Convection

Mesosphere

Solid lower mantle

Outer core

• Circulation of the liquid __

• Generates earth’s magnetic field

• Can reverse

Inner core

Solid

Lithospheric plate

• Made of the crust & the uppermost mantle

• Rigid layer broken into _____ that move along slowly

• Carried by convection within the ductile asthenosphere

Alfred Wegener

German paleoclimatologist

• Made the Continental drift hypothesis

• Believed in the concept of a supercontinent (Pangea) that drifted apart

Continental Drift Hypothesis

Continents were once together as a supercontinent ⇒ Pangea

• Pangea drifted apart around 200M yrs ago

• Continents slowly drift, plowing through the ocean floor ahead (1915)

Pangea

Supercontinent, “all earth”

Pangea Rifting

Occured during the Phanerozoic eon

• Paleozoic Era

  • Permian Period

• Mesozioc Era

  • Triassic Period

• Early Cenozoic Era

  • Jurassic Period

  • Cretaceous Period

Pangea assembled

Paleozoic Era

• Permian Period

Pangea remains assembled

Beginning of the Mesozoic Era

• Triassic Period

Shape of the Pengea

A C shape

Pangea slowly rifted away

Early Cenozoic Era

• Jurrassic & Cretaceous Period

Panthalassa superocean

Surrounds the Pangea

Tethys ocean

In the indent of thr Pangea

Laurasia

Northern hemisphere of Pangea

• North America, Greenland, Europe, & Asia

Gondwana Land

Southern hemisphere of Pangea

• South America, Africa, India, Australia, & Antarctica

Evidence for Continental Drift Hypothesis

• Geographical fit of the continents 

• Matching precambrian cratons

• Matching old Phanerozoic mountain belts

• Matching fossils of terrestrial plants & animals

• Matching paleoclimate belts

Old Precambrian crust (cratons)

Match across the now-separated continents (South America & Africa)

Shelf slope break

Mapping shows a significantly better fit via aligning with it

Matching eroded mountain belts

Seeing if continents match by their relative age & style deformation

• Scandinavian caledonides ⇒ EU

• Appalachians ⇒ NA

Appalachians

NA

Scandinavian caledonides

EU (mountain belt)

Glossopteris Trees

An extinct terrestrial flora (plants)

• Large & heavy, too large to be carried

• Found on many continents

  • Implying they were once joined together

Mesosaurus

Extinct terrestrial fauna (animals)

• Small freshwater reptile

• Found in separated continents

  • Implying they were once joined together

Matching Paleoclimate Belts

Many evidence seen in the rock record

• Perserved in fossil tree & leaves, glacial deposits, etc

• Temperate, Arid, Tropical, & Polar belts

Temperture Belt

• Fossil leaves with scalloped edges

• Fossil tree trunks with seasonal growth rings

Tropical Belt

• Fossil leaves with smooth edges

• Thick coal beds from vast tropical swamp

• Coral reefs

Arid Belt

• Sand dunes & evaporites

Polar Belt

• Till & striated bedrock